Chinese migrants aged over 50 have doubled in percentage terms, rising from 19.6 per cent in 2006 to 39.9 per cent last year.

"That's a major concern in terms of two things: we really need skilled migrants and we really don't want to add to the ageing of the population."

Professor Spoonley said there should be a cap on the number of visas issued to older immigrants, especially in the non-business and skill categories.

Ageing baby-boomers were already pushing up numbers of the elderly in the country, with those aged 65 and over already making up 14 per cent of the population.

Last year, 86,420 New Zealanders aged over 15 left the country permanently, 71.7 per cent of them aged between 15 and 49, according to Statistics New Zealand.

Numbers in the 65-plus age group in New Zealand have increased by 43,100 since 2011, while fertility and mortality rates have dropped.

"We don't want to contribute to that by bringing in older migrants, regardless of what country they come from," he said. "I wouldn't want to see a significant increase in the family approvals at the expense of skilled and business categories."

In 2006, significantly more Chinese nationals gained residency through the business and skilled categories, and they were now sponsoring their parents, said Professor Spoonley. "Given the size of the community and the fact many arrived in their 20s and 30s, you would expect them about now to be concerned about parents who have been left in China and now need close family members close by."

Immigration's "centre of gravity" rule allowed parents to be sponsored if the number of adult children living in New Zealand was equal to or exceeded those in any single country.

China by far outnumbered all other countries in the family sponsored stream and parent immigration categories. Nearly all China nationals who are permanent residents can therefore sponsor their parents because of that country's one-child policy.

New Zealand First MP Denis O'Rourke, who is campaigning for an immigration review of the family policy, said numbers of parents from China were 120 per cent of its skilled migrants. No other country exceeded 24 per cent of their skilled migrant stream, he said.

"Parent category migrants after 10 years' residency, without any requirement to work, can collect full NZ Super at 65 years, the same as Kiwis who have lived and worked in New Zealand all their lives," Mr O'Rourke said. "Life expectancy after 65 is about 20 years, and that's about $350,000 in NZ Super for every parent migrant."

Immigration Minister Michael Woodhouse said there was an annual cap on the parent category visas, although it did not have any age restrictions.

The parent category had been changed last year after a review and the "centre of gravity" provisions had been removed.

There were 1080 (17.9 per cent) of migrants aged 50 and over from the United Kingdom and 544 (10.4 per cent) from India. China was New Zealand's second-largest source country for permanent migrants, ahead of India but behind Britain.